| As an important measure to solve the problem of soil erosion,vegetation restoration and construction have greatly improved the fragile ecological environment of the Loess Plateau.However,there is a huge contradiction between the limited carrying capacity of water and soil resources in the Loess Plateau and the need for vegetation restoration.The limited water and soil resources are not enough to support the whole area to achieve vegetation coverage.To solve this problem,choose a suitable regional environment and have excellent corrosion resistance.Effective vegetation measures are of great significance to regional environmental protection and high-quality development.Vegetation characteristics such as vegetation type,root system and distribution pattern are important factors affecting the effect of vegetation on erosion control.In this study,the common crops of the Loess Plateau,millet and herb alfalfa,were used as the research objects.Millet)mulching,alfalfa root growth and alfalfa planting pattern change,the effects of three vegetation characteristics changes on soil erosion on the slopes of the Loess Plateau,the main conclusions are as follows:(1)The mulching of full-growth millet and alfalfa has different effects on slope erosion.In comparison,the anti-erosion effect of herb alfalfa is better than that of crop millet.With the extension of the growth period,the runoff of millet and alfalfa covered slopes is delayed,the initial runoff time of the slopes continues to prolong,the runoff intensity and sediment production intensity of the slopes continue to decrease,and the runoff sediment and sediment content of the slopes continue to decrease.With the continuous reduction,the benefits of vegetation flow and sediment reduction were continuously improved,and the sediment reduction benefits of the two types of vegetation were better than the flow reduction benefits.Compared with the level bare land CK,under the condition of 80 mm/h rain intensity,the initial runoff time of 3°-15°millet-covered slopes in the whole growth period was prolonged by 29.52-445.00%,and the average yield of Sd millet-covered slopes during the grain filling period was prolonged.Compared with the Sa in the seedling stage,the flow intensity decreased by 28.70-33.33%,the average sand production intensity of the Sd millet-covered slope in the grain filling stage decreased by 75.0-78.5%compared with the Sa in the seedling stage,and the total runoff of the millet-covered slope in the whole growth stage decreased by 2.42-22.17 L/m~2,the total amount of sediment decreased by 39.86-359.82 g/m~2,the runoff sediment content decreased by 0.41-5.24 g/L,and the runoff reduction benefit of millet covering the slope during the whole growth period was 4.16-48.24%,the sediment reduction effect was17.35-84.0%;under the condition of 90 mm/h rain intensity,the initial runoff time of 5°-20°alfalfa covered slopes in the whole growth period was prolonged by 2.97-96.00%,and the S4 purple flower in the pod setting stage was prolonged by 2.97-96.00%.The average yield intensity of alfalfa-covered slopes decreased by 59.64-84.02%compared with that of seedling stage S1,and the average sand production intensity of alfalfa-covered slopes in pod-setting stage S4 was 87.82-91.31%lower than that of alfalfa-covered slopes in seedling stage S1.The total amount of runoff on the surface decreased by 7.69-50.56 L/m~2,the total amount of sediment decreased by 197.57-1145.02 g/m~2,and the sediment content in the runoff decreased by 0.54-12.35 g/L.The flow reduction benefit of the slope is10.36-85.79%,and the sediment reduction benefit is 15.34-94.48%.(2)The roots of alfalfa in the whole growth period regulated the slope erosion process to different degrees,but compared with the aboveground tissues of alfalfa,the anti-erosion effect of alfalfa roots was relatively weak.The existence of alfalfa root system prolonged the initial runoff time on the slope surface,and with the growth of the root system,the delaying effect became more obvious.Under the condition of 90 mm/h rain intensity,compared with the leveling bare soil CK,the initial runoff time of the 5°-20°alfalfa root-retained slope in the whole growth period was prolonged by 0.25-40.00%.From the seedling stage to the pod setting stage,the runoff intensity and sediment production intensity of the alfalfa root-retained slope surface continued to decrease,the total amount of runoff,the total amount of sediment and the runoff-sediment content of the alfalfa root-retained slope surface gradually decreased,and the root system The benefits of flow reduction and sediment reduction were gradually improved.The average flow yield intensity of S4 alfalfa root-retaining slopes in the pod-setting stage was 16.71-30.45%lower than that of the seedling stage S1.S1 decreased by 23.82-44.78%.Compared with the leveled bare land CK,the total runoff of the alfalfa root-retained slope was reduced by0.96-20.54 L/m~2,and the total amount of sediment was reduced by 10.19-313.16 g/m~2.The runoff sediment content decreased by 0.17-2.23 g/L,the runoff-reducing benefit of alfalfa root-retaining slope in the whole growth period was 1.29-34.86%,and the sediment-reducing benefit was 0.87-49.97%.(3)The alfalfa covered slopes with different vegetation patterns at the pod setting stage all have the functions of regulating the process of flow and sediment production on the slope,changing the relationship between water and sediment on the slope,and storing water and soil.The anti-corrosion effect is expressed as equidistant SS>downhill LS>slope middle MS>uphill US.Therefore,in the process of vegetation measures,the layout pattern of equidistant SS can be given priority.Covering slopes with alfalfa in different patterns can delay the runoff time,inhibit the runoff and sediment production process,reduce the runoff intensity,sediment production intensity and peak sediment production intensity,and reduce the total amount of slope runoff,total sediment and runoff content.sand volume.Compared with the leveled bare land CK,from the US treatment to the SS treatment,the alfalfa coverage of each vegetation pattern prolonged the initial runoff time of the slope by5.61-212.00%,and the average runoff intensity of the alfalfa covered slope of each pattern decreased by 7.18-83.77%,the average sediment yield decreased by 12.62-85.69%,the peak sediment yield decreased by 11.47-56.73%,the total runoff of each vegetation pattern alfalfa covered slope decreased by 5.33-49.89 L/m~2,the total sediment The amount of sediment decreased by 115.09-657.49 g/m~2,and the runoff sediment content decreased by0.26-2.22 g/L.From the US treatment to the SS treatment,the benefits of alfalfa-covered slopes in reducing flow and sediment increased continuously.Compared with CK,the flow-reducing benefits of alfalfa-covered slopes in each vegetation pattern were7.19-84.67%,and the sediment reduction benefits were 12.62～86.48%. |
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